Allow EDNS to be used when making requests in xfrin

Allow EDNS to be used when making requests in xfrin

This allow for the EDNS options EXPIRE and NSID to be sent when
when making requests.  The existing controls controlling whether
EDNS is used and whether EXPIRE or NSID are sent are honoured.

Adjust the expected byte counts in the xfer system test to reflect
the EDNS overhead.  Adjust the dig call to match named's behavior
(don't set +expire as we are talking to a secondary).